[lib][rr_graph] return unlock_storage since it is needed by OpenFPGA

Author: amin1377

libs/librrgraph/src/base/rr_graph_builder.h

@@ -401,6 +401,16 @@ class RRGraphBuilder {
         return node_storage_.count_rr_switches(arch_switch_inf, arch_switch_fanins);
     }
 
+    /**
+     * @brief Unlock storage; required to modify an routing resource graph after edge is read
+     * @note This function is used by OpenFPGA and currently doesn't have any use in VPR code.
+     */
+    inline void unlock_storage() {
+        node_storage_.edges_read_ = false;
+        node_storage_.partitioned_ = false;
+        node_storage_.clear_node_first_edge();
+    }
+
     /** @brief Reserve the lists of nodes, edges, switches etc. to be memory efficient.
      * This function is mainly used to reserve memory space inside RRGraph,
      * when adding a large number of nodes/edge/switches/segments,